Study On Modifying The Photocatalytic Properties Of Anatase TiO₂?101? Surface By Doping Transition Metals

Anatase TiO₂,an important semiconductor photocatalytic material,is widely used in the fields of solar energy conversion and environmental purification,due to its advantages,such as non-toxicity,economy,good stability,and high catalytic activity.However,because the bandgap width of anatase TiO₂ is relatively wide,it can only make little use of the power in visible light.Therefore,it is necessary to make investigations to modify its properties so as to improve its photocatalytic activity.Actually,transition metal doping is considered as one of the most convenient and efficient methods.In this thesis,based on the planewave ultrasoft pseudopotential method of the density functional theory,we carried out a systematic theoretical investigation on modifying the photocatalytic properties of anatase TiO₂?101?surface via doping seventeen transition metal neutral atoms,including ten 4d transition metals of the same period such as Y,Zr,Nb,Mo,Tc,Ru,Rh,Pd,Ag,and Cd,and seven common transition metals of the same group such as Fe,Ni,Pd,Pt,Cu,Ag,and Au.By analyzing the related electronic structure and optical properties of the doping systems,we obtain the following research results:?1?The photocatalytic activity of anatase TiO₂?101?surface can be changed differently by doping different transition metal atoms,which is closely dependent on the bandgap width,the Fermi energy location,the impurity energy levels location,and the electron configuration of the outermost shell of the transition metal atoms.?2?The optimal manners of doping on anatase TiO₂?101?surface are different for different transition metal atoms.It is found that,Y,Ru,Rh,Pd,Ag,Ni,Cu,and Au prefer adsorption doping at O atoms of the anatase TiO₂?101?surface,Tc,Cd,Fe,and Pt prefer to adsorb on Ti atoms of the anatase TiO₂?101?surface,and Zr,Nb,and Mo prefer doping in the cavities of the anatase TiO₂?101?surface.?3?Doping certain transition metals can make Fermi levels move into the conductance band,or band gap,and induce extra impurity energy levels in the conductance band,valence band,or band gap,and also may suppress the band gap,which are beneficial to improving the visible light response of TiO₂?101?surface in the different ways.In addition,the impurity energy levels mainly come from the contribution of the d electronic states in the transition metal atoms.?4?The visible-light response intensity of TiO₂?101?surface doped with 4d transition metals will decrease with the increase of the atom numbers of dopants excepting for Ag.Ag has a large atomic number,but its doping can also significantly improve the visible-light response of TiO₂?101?surface,which may be caused by the special electron configuration of its outermost shell.?5?For transition metals of the same group,Fe,Cu and Ag doping have the best visible-light response,which is mainly because their Fermi levels are moved into the conductance band,thereby inducing intraband transition.Moreover,Ni doping,with its new absorption edge having a red shift,can efficiently improve the visible-light response of TiO₂?101?surface.In summary,the dependence of the macroscopic catalytic activity on both the electronic structures and the optoelectronic properties is uncovered by the systematic study on modifying the photocatalytic activity of anatase TiO₂?101?surface via doping different transition metals.This research should be an instructive reference for designing TiO₂?101?photocatalyst and improving its capability,and also be helpful for understanding doping transition metal atoms in other materials.